Space particle smacks into Sentinel-1A satellite, leaves sizable dent

ESA's Sentinel-1A satellite has been
struck by a space particle while orbiting at a height of 700 km (435
miles) above the Earth. The
particle is estimated to have measured only a few millimeters across,
yet the impact caused a dent in the solar panel of the spacecraft 40
cm (15.7 inches) in diameter. It is not yet known whether the debris
was manmade or natural in origin.

The Sentinel-1A satellite is tasked
with monitoring the health of Earth's oceans, highlighting changes in
the use of land, and providing data for emergency response efforts in
the wake of natural disasters, as part of the European Union's
Copernicus Program.

At 17:07 GMT August 23, mission operators detected a minute drop-off in power output
from the satellite's twin solar panels, which, combined with a slight
alteration in the probe's orbital trajectory, indicated that the
spacecraft may have been struck by a piece of orbital debris. To
confirm the impact, the team decided to switch on the probe's side-facing cameras.

The cameras had been mounted on either
side of the satellite in order to provide visual confirmation that
Sentinel-1A's delicate solar arrays had successfully deployed in the
hours following its launch. Having completed their initial task
admirably following orbital insertion in April 2014, mission
controllers had deactivated the cameras, with no intention of turning
them back on again.

Following the events of the 23rd, the
cameras were commanded into life once more, granting technicians a
clear view of where the particle had struck the 10 m (32.8
ft) solar array, leaving the large dent in the process.

"Such hits, caused by particles of
millimeter size, are not unexpected," comments Holger Krag, head of
ESA's Space Debris Office in Darmstadt, Germany. "These very small
objects are not trackable from the ground, because only objects
greater than about 5 cm can usually be tracked and, thus, avoided by
maneuvering the satellites."

Artists impression of Sentinel-1A in space(Credit: ESA/ATG medialab)

Thankfully, Sentinel-1A has emerged
from the ordeal intact, and able to continue its mission unhindered.
However, space debris represents a very real problem for those hoping
to operate in the increasingly crowded environment of low-Earth orbit
(LEO), which is frequented by swarms of telecommunication, military
and basically every other form of satellite.

Decades of orbital operations has led
to over 500,000 pieces of manmade debris larger than a marble
whizzing around in LEO. This number gets a lot higher the smaller the
gauge of debris. No matter how small a piece of space trash is, when
it's moving at over 17,500 mph (28,162
kmph)it is going to
damage whatever it hits, with potentially catastrophic results.

These collisions do happen. In the past
whole satellites have collided with one another, creating vast clouds
of debris capable of crippling a spacecraft, or in a worst-case
scenario, a manned outpost such as the International Space Station.

Space agencies across the globe are
aware of this growing issue, and regulations have been put in place
requiring satellites and launch vehicles to be designed with a the
capacity to either de-orbit themselves, or to push themselves into a
distant "graveyard" orbit.

There are also numerous concepts under
development with the potential to de-orbit the multitude of debris
and derelict satellites already present in LEO. Netting and
harpooning space junk are two techniques that could be employed to
de-clutter LEO, while using gas clouds and lasers to zap the orbital
trash are also under consideration.

Hopefully, these new technologies will
reduce mankind's inevitable footprint in orbit, and avoid a Kessler effect, whereby debris in LEO causes a cascade of collisions that
would render the operation of satellites in certain orbits
impossible.